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How phone determines what UDP port to use

How phone determines what UDP port to use

How phone determines what UDP port to use

(OP)

We have a new site off shore, no local gateways, phones register back to core, media goes through gateway at core pbx site.

All NRs are setup to use 16384-32767 for UDP.

When phone goes off hook, it's trying to use ports in the 40xxx range.

Why would this be? Is it a network configuration? I'm thinking it might be in the QoS ACL.

- Stinney

“The man who asks a question is a fool for a minute, the man who does not ask is a fool for life.” - Confucius

RE: How phone determines what UDP port to use

What kind of phone? h323 use what's in the network region. SIP is what's defined in the settings file.

RE: How phone determines what UDP port to use

(OP)

We figured this out just before I left for vacation.

You are correct, the NR ranges are what determines what the phone uses for RTP/Audio.

We discovered that the phone wasn't actually fully registered and the port we saw was the PBX trying to complete a registration with the phone. Apparently to establish connection/registration with the phone (H.323) the PBX uses dynamic ports 49152-65535.

Once we realized what was happening, we opened the firewall to allow these ports and the phones registered. We thought we only needed the 1719/1720 for the registration to the procr.

- Stinney

“The man who asks a question is a fool for a minute, the man who does not ask is a fool for life.” - Confucius

RE: How phone determines what UDP port to use

I think what you might be referring to is the little bit of Avaya magic in H323. At the bottom of page 3 of your network region, there's a port range that defaults to 61440-61444. For subnets defined in the network region, CM reaches out on that port range to establish a TCP socket with phones and juggles'em down to 1719/1720.

You can turn it off. The point of it is when the WAN recovers at a site with, say, 1000 phones, your core firewall in front of CM doesn't flip out and see a flood of 1000 connections from a remote subnet to 1 IP and mistake it for a DDOS attack. If that switch is set to yes, then yeah, you need those FW ports open from CM outward to the site!

RE: How phone determines what UDP port to use

(OP)

The port range that you can force the NR to use wasn't being used. From what Avaya has stated, unless you use this setting in the NR, the PBX uses any of the dynamic ports in the 49152-65535 range for registration of the station.

- Stinney

“The man who asks a question is a fool for a minute, the man who does not ask is a fool for life.” - Confucius

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